RNA-unwinding and RNA-folding activities of RNA helicase II/Gu--two activities in separate domains of the same protein.
The human RNA helicase II/Gu protein (RH-II/Gu) is a member of the D-E-A-D box protein family. It is a unique enzyme, which possesses an ATP-dependent RNA-unwinding activity and has an RNA-folding activity that introduces an intramolecular secondary structure in single-stranded RNA. This report shows that these two enzymatic activities are distinct. ATP[S], GTP and low concentrations of ATP enhance the RNA-folding activity of RH-II/Gu but not the RNA-helicase activity. High concentrations of ATP are required for the helicase activity but are inhibitory to the RNA-folding activity. Mg2+ is required for the helicase activity but not for the RNA-folding reaction. Affinity-purified anti-(RH-II/Gu) polyclonal Ig inhibit the RNA-unwinding activity but not the folding activity. Mutations of the DEVD sequence, which corresponds to the DEAD box, and the SAT motif enhanced RNA-folding activity of RH-II/Gu but completely inhibited the RNA-helicase activity. A mutant that lacks the COOH-terminal 76 amino acid residues, including the four FRGQR repeats, had unwinding activity but did not catalyze the folding of a single-stranded RNA. The two enzymatic activities of RH-II/Gu reside in distinct domains. Amino acids 1-650 are active in the RNA-unwinding reaction but lack RNA-folding activity. Amino acids 646-801 fold single-stranded RNA but lack helicase activity. This report shows distinct RNA-unwinding and RNA-folding activities residing in separate domains within the same protein.
Valdez
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BC
Department of Pharmacology, Baylor College of Medicine, Houston, TX 77030, USA. bvaldez@bcm.tmc.edu
Henning
D
D
Perumal
K
K
Busch
H
H
D000251:Adenosine Triphosphatases / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000906:Antibodies / Q000276:immunology / Q000494:pharmacology; D015153:Blotting, Western; D004591:Electrophoresis, Polyacrylamide Gel; D000939:Epitopes / Q000737:chemistry / Q000276:immunology; D004926:Escherichia coli / Q000235:genetics; D006160:Guanosine Triphosphate / Q000378:metabolism; D006801:Humans; D008274:Magnesium / Q000494:pharmacology; D016297:Mutagenesis, Site-Directed / Q000235:genetics; D009687:Nuclear Proteins / Q000737:chemistry / Q000378:metabolism*; D009690:Nucleic Acid Conformation; D010446:Peptide Fragments / Q000378:metabolism; D012313:RNA / Q000378:metabolism; D020365:RNA Helicases; D012316:RNA Nucleotidyltransferases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism
D000906:Antibodies; D000939:Epitopes; D009687:Nuclear Proteins; D010446:Peptide Fragments; D011993:Recombinant Fusion Proteins; D012313:RNA; D006160:Guanosine Triphosphate; D000255:Adenosine Triphosphate; D012316:RNA Nucleotidyltransferases; D000251:Adenosine Triphosphatases; D020365:RNA Helicases; D008274:Magnesium